In recent years, a linear motion guide unit has been used in sliding sections of semiconductor fabrication systems, machine tools, assembling apparatus, robots, etc. As a result of acceleration of a reduction in size and sophistication of electronics, strong demand has arisen for the linear motion guide unit to be small or compact in size, to provide high accuracy and high load capacity, and to be usable for applications involving high speed or high acceleration and deceleration. Conventionally, strong demand has arisen for a finite linear motion guide unit to be small in size, to provide high load capacity, to be usable for applications involving high speed or high acceleration and deceleration, and to provide easy assembly, for example. In order to prevent the retainer from straying or wandering in relation to the guide members, various mechanisms for preventing the retainer from straying or wandering in the longitudinal direction of the guide members are available for the finite linear motion guide unit. For example, the finite linear motion guide unit disclosed in Japanese Patent Application Laid-Open No. 2003-28157 is configured such that a pair of racks disposed on respective guide members, and a pinion disposed in a plate-like retainer mesh with each other to correct the relative position of the retainer, thereby preventing the retainer from straying or wandering.
According to the cross-roller finite linear motion guide unit disclosed in Japanese Patent Application Laid-Open No. 2012-202458 of the corresponding patent application filed by the applicant of the present invention, the retainer for retaining rollers serving as rolling elements between the guide members is reduced in longitudinal deflection or bend, and roller-retaining means are provided in respective windows of the retainer plate to thereby reduce the disposition pitch of the rollers, thereby increasing the number of the rollers disposed over a predetermined length. The retainer plate is formed of a synthetic resin integrally with a holder portion into which the pinion is fitted. The retainer plate has the windows into which the respective rollers are inserted such that the axes of the rollers are orthogonal to the longitudinal direction and inclined from a main surface at an angle of 45°. A portion of the wall surface of each window which faces the end surface of the roller is formed into a bearing edge which covers a portion of the end surface of the roller. Rims are formed at longitudinal opposite side ends, respectively, of the retainer plate in such a manner as to extend along the longitudinal direction and to protrude from the main surface, for reducing deflection.
The sliding device disclosed in Japanese Patent Application Laid-Open No. 2006-183821 restrains a micro-slip phenomenon without reducing the number of rolling elements retained by a rolling-element retainer. In the sliding device, the retainer for retaining the needle rollers is formed into a V-like shape. The V-shaped retainer is configured such that a first retainer portion for retaining one rolling-element group and a second retainer portion for retaining the other rolling-element group are connected at a connection portion and such that an engagement member is provided in a substantially central region of the connection portion. Protrusions of the engagement member are sequentially engaged with recesses formed in a shaft and a load path member which forms a load path in cooperation with the shaft.
However, in the cross-roller finite linear motion guide unit disclosed in Japanese Patent Application Laid-Open No. 2012-202458, in order to increase the width of contact between a roller and the raceway surface by increasing the depth of the raceway groove, in the band-plate-like retainer plate, the elliptic windows in which the rollers are disposed respectively have the respective bearing edges for retaining the rollers, and the pinion-and-holder assembly is attached into an opening of the retainer plate. Also, in the cross-roller finite linear motion guide unit, the retainer plate is formed of a synthetic resin integrally with the holder portion for holding the pinion; rims are formed respectively on longitudinal sides of the retainer plate located on opposite sides with respect to the width direction for reducing deflection of the retainer plate; and detachment of the rollers from the retainer plate in the course of assembly is structurally prevented. However, the retainer plate is not formed into a V-like shape; i.e., an idea of increasing a rated load is not employed. Meanwhile, the retainer disclosed in Japanese Patent Application Laid-Open No. 2006-183821 is formed into a V-like shape. However, a rack-and-pinion mechanism is not employed as a retainer straying prevention mechanism. Instead, the engagement member has a large number of protrusions formed on its outer cylindrical surface, and recesses to be sequentially engaged with the protrusions are formed along the load path. This structure involves complication in manufacture.